Here's What Could Happen When a Small Drone Meets a Big Airplane

A California Highway Patrol's helicopter’s near-miss with a drone over Martinez, Calif. on Saturday is raising hackles. The drone was flying above 700 feet, according to the Chronicle  — nearly twice the legal altitude — and the operator may face charges.

We often hear that drones are a potential threat to aircraft, but to laymen with neither a pilot’s lic ense nor a degree in aeronautical engineering, it suggests a puzzle: The drones most of us have encountered are handheld toys made chiefly of foam and weighing roughly as much as a Frisbee. How can they endanger a professionally engineered aircraft weighing several tons?

[jump] “First thing: They’re not just foam,” says John DuGan, owner of the helicopter tour company Bay Aerial.

The word drone is applied to a lot of different devices because of its marketing value. It may refer to feather-light quad copters made of NERF-like material, but drones weighing up to 55 pounds can legally fly up to 100 mph —quite a weighty midair surprise for a pilot.

(“I hate drones,” DuGan adds. “I’ll be the first to admit they’re cool, but they put lives in danger.” He says he had a near-miss himself with a drone over Redwood City this year and didn‘t know it until later.)

The second thing to consider is that aircraft are designed to be lightweight. They have to be if they want to get airborne in the first place. Steel is sturdy, but composite materials like fiberglass handle better in the air. And few non-military aircraft are designed to be struck by a 50-pound chunk of solid material mid-flight, no matter what it’s made of. Only in the last few years have aeronautical engineers had to consider such a possibility.

Finally, a simple physics lesson applies. With a mid-air collision, the size and velocity of both objects matter. A drone might be relatively light and not going all that fast (depending on the model), but a lot of force can still result from the wallop of a bigger and heavier machine.

“A jetliner traveling at 250 miles per hour hitting a 25-pound UAV would create a huge amount of force — around 40,000 pounds of it,” writes Patrick Smith, an airline pilot and blogger.

Add it all up and it’s possible for mere plastic to snap a rotor or bust a windscreen at 700 feet. Not to mention that drones have a habit of sneaking up on you.

“You’re not expecting to encounter a mechanical device at that altitude,” says Marlon Varin, a sergeant with CHP’s air operations. Mostly, they’re on the lookout for birds, which at least have the sense to get out of the way (usually).

Privately, some drone enthusiasts and manufacturers scoff at the idea that a drone could pose a threat to an airliner, but helicopters are another matter. The FAA keeps helicopters at above 500 feet — out of drone territory, except in the case of yahoos who flout the rules like this weekend’s Martinez flyboy — but they are permitted to fly lower under certain circumstances.

“A news helicopter may want to hover over a traffic accident, for example,” says SFO spokesman Doug Yakel. “They can do that if they’re in contact with our patrol tower.”

That can take them down into the range of even those drone flyers scrupulously obeying the law, and into places where those operators may not expect an aircraft.

This is the kind of thing that might keep Amazon Air engineers up at night. Jeff Bezos insists that the future is one where hundreds of thousands of drones taxi through our skies every day (delivering Amazon products, of course). They’ll stay below that all-important 400-foot barrier, but that won’t keep them clear of all larger air traffic all the time.

But drone insiders contend that innovation will soon fix that problem as well. There’s talk of a potential drone air-traffic control system with drones that ping cell phone towers, of drones with transponders that detect nearby craft and automatically get out of their airspace, and of apps that update operators about hazards.

It‘s a lot to promise. But technology is on the move, and the genie isn‘t going back into the bottle anytime soon.

“When planes were first introduced, people called them death machines, and they were terrified of them flying over their homes,” says Armin Monajemi, owner of Drones Plus in Santa Clara. “It was the same with helicopters, and now drones.”

Drones Plus is less than two years old but has locations in more than 20 cities. Monajemi’s store opened four months ago, and he says he gets customers from as far away as Sacramento. Monajemi, who is also a single-engine airplane pilot, says that this is all just the growing pains of a new technology.

That’s the droner’s point of view, anyway. Hopefully they’re right. If the Bezoses of the world get their way (and they usually do), this is just the start, and there’s only so much air to go around up there. 

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